In the printing industry a wide variety of printing methods are employed. Printing methods such as lithographic, flexographic, screen and gravure printing commonly involve preparing an image-bearing printing surface before commencing printing. Such printing surfaces are often prepared in an imaging device which uses an imagewise addressable radiation source to selectively convert or transform areas of a printing precursor.
In some cases the printing surface is directly ready for use following imagewise conversion. In most cases further processing is required. Processing may include further exposure to radiation, heating, chemical development, chemical etching, a variety of other processes or combinations thereof. In other imaging industries such as the direct imaging of printed circuit boards, imaging devices are commonly coupled with a processor of some description for further processing or development of the imaged article.
In the graphic arts industry, imaging and processing steps are usually performed by separate equipment, often provided by different manufacturers. For example, lithographic plates, and more particularly thermal lithographic plates are typically imaged in platesetter devices which use high power radiation sources such as lasers for imaging. After imaging, plates are removed from the platesetter and either manually or automatically conveyed to a processor. For negative working thermal plates, processing typically includes a preheat step, in which the plate is uniformly heated to crosslink imaged areas, followed by development in a chemical solution that removes non-imaged areas. The plates may be post-baked to improve their run length on press.
It is important to heat plates evenly during processing. The required preheat consistency over the plate surface for a negative working thermal plate is preferably in the range of 5° C.-10° C. and most preferably less than 2° C. It is also important to maintain any chemical solutions used in developing plates in good condition. In most instances, the chemical action which occurs during development of a plate weakens or contaminates the chemical solutions used.
Plate processors which provide automatic replenishment of developer chemistry and active control of preheat have been described and/or marketed by vendors. The inventor has observed that prior art processors equipped with such automatic function do not integrate well with imaging and processing systems.
WO 01/29620 to Haley et al., describes an integrated processor which has a pre-heat oven, a developer section, and an optional post-bake section. Preheat is controlled in one embodiment by varying the speed with which plates pass through the preheat section or the disposition of heating elements in response to a trigger such as the plate entering the preheat section. Further measurements of the plate such as width provide additional control inputs for maintaining even heating.
Stein et al., U.S. Pat. No. 5,716,743 to describes a system for monitoring the condition of a developer solution by measuring a number of parameters. Measurements such as conductivity and temperature of the developer solution are used along with knowledge of how the chemistry is degraded by processing particular formats and types of printing form. The system determines whether to dilute the developer solution with water or to add more developer.
There remains a need for a better apparatus and methods for processing imaged articles. There is a particular need for such apparatus and methods which can automatically accommodate articles of different dimensions and/or types. The printing industry has special need for such apparatus and methods.